1. Field of the Invention
This invention relates to intraocular lenses and in particular to intraocular lenses having the capability for insertion into the anterior or posterior chamber of the eye and having the capabilities of universal fit.
2. Problems In the Art
Present methods of surgically treating cataracts involve removal and replacement of part or all of the natural eye lens with an artificial intraocular lens. The artificial lens is designed to come as close as possible at mimicking the natural lens and therefore must be securely and stably placed within the eye.
To facilitate the insertion and securement of the artificial lens, support structure must be associated with the artificial lens. Some devices which are still used in certain cases, require suturing the support structure to suitable portions of the eye to hold the lens in place. Aside from the obvious complexity of such implantation, this method makes removal or adjustment of the lens extremely difficult and subjects the eye to additional damage.
Developments led to a less traumatic intraocular lens which utilizes arms or extensions from the lens which fit within the natural boundaries or walls of the eye and hold the lens in place by contact and compressive forces. While some of these devices still utilize sutures to finally secure them in place, many are now being used which, by virtue of their resilient compression and contact with parts of the eye, are non-sutured and self-securing.
Typical examples of such a device are disclosed in Callahan, U.S. Pat. No. 4,363,143 and Kelman, U.S. Pat. No. 4,370,760. All utilize flexible arms extending from the lens body to resiliently hold the lens in place.
Devices such as Sheets, U.S. Pat. No. 4,328,595, utilize flexible support loops having proximal ends fused or inserted into the lens body.
Although there are many different types of intraocular lenses in use and available for use, problems within the art still exist.
Many existing lenses are usable for certain size eyes and therefore must be manufactured in many different sizes. This requires surgeons to keep a large inventory of lenses. Secondly, many of the devices are specifically designed for either anterior placement or posterior placement. Again, this requires the surgeon to have the requisite inventory to satisfy the needs of various patients. Existing, so called "universal lenses" (Duolens, Shepard Universal, Pannu) are either excessively fragile, difficult to insert in one or both locations, or lack vaulting to separate the lens from the iris or capsule. Several are totally dependent on a single filament for support and if fractured would result in the collapse of the lens requiring immediate removal.
Another major problem with existing intraocular lenses involves contact and irritation of the eye by the support structure of these devices, or even the lens itself. This might result from the position of the lens once implanted or may result from contact of the support structure. One method by which some prior art devices attempt to minimize such problems is by having support structure which biases or resiliently urges the lens body posteriorly in an attempt to force the lens body back towards the posterior capsule and away from the iris.
A disadvantage produced by holding the lens towards the posterior capsule exists in the fact that once implanted, additional surgery is many times needed. Modern methods of surgery increasingly utilize lasers to facilitate this surgery. If the lens body is biased towards the posterior capsule, as is the case with many of the existing devices, laser surgery of the posterior capsule is more difficult, if not precluded, and the lens is exposed to a great risk of damage. An elevation slightly from the posterior capsule facilitates YAG laser capsulotomy while still avoiding the risk of pupil capture. It also allows sufficient clearance for YAG laser photocoagulation.
With many self-supporting intraocular lenses, the support structure does not sufficiently have the ability to compress to different sizes of eyes, while at the same time both minimizing compression forces and preventing tilt or torque and presenting relatively easy insertion capabilities and sufficient fixation of the lens body so that pupil capture is prevented.
Another disadvantage of many of the present devices is that the stability of the lens is sacrificed in order to obtain more flexible, universal fit lenses. Likewise, many of the present devices cannot be easily insertable and maneuverable with one instrument and many are totally dependent for support on one fragile strut or filament.